Article of bonded granular material and method of making the same



April 26,1927.

H. c. MARTIN ARTICLE OF BONDED GRANULAR MATERIAL AND METHOD OF MAKING THE SAME Filed NOV. 15, 1924 INVENTOR means of Patented Apr. 26, 1927.

STATES PATENT OF E- HARRY o. MARTIN, or NIAGARA FALLS, NEW YORK, AssIGNOR TO THE cARRORuNnUm. COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION orrEN'NsYLv Nm ARTICLE or BONDED GRANULAR Application filed November 13, 1924. Serial No. 749,773.

The present invention relates to articles of bonded granular material and their process of manufacture, this application being a continuation in part of my co-pending application, Serial N 0. 690,7 06, filed February 5, 1924.

IVhile this invention is applicable to various articles of bonded granular material, it will first be described with particular reference to its embodiment in abrasive disks of the type used on machines known as disk grinders for the grinding of fiat surfaces on metals and other materials. must have a relatively high degree of porosity-to prevent glazing and hence the proportion of the binder with respect the abrasive grains is limited and the amount of agglomerating pressure is also limited. It is important, therefore, that the bond between the abrasive grains possess a high degree of mechanical strength. Such disks usually-consists of a. paper or cloth backing or body coated with alayer of abrasive material bound to the backing b'y glue'after the manner of ordinary sand paper. and emery cloth. Their use is limited, due to the fact that whenusing a glue binder, w thin and the disks do not, therefore, possess very much durability when called upon to do heavy work or remove large quantities of metal. I I have discovered that a very efiicient disk of superior qualitycan be made by the use of a mixture of abrasive grains and a synthetic resin such as a phenol resin, The phenol resin which I prefer to employ is known under the trade name of redmanol. Redmanol is a synthetic resin which consists of a phenolic body mixed with a hardener. This hardener is a. formaldehyde compound such as hexamethylenetetramine. I prefer to use the redmanol in a powdered form. v I

In the'accompanying drawings, forming part of this specification, Figure l is a sectional view of a suitable mold which may be employed in the manufacture of the disks;

Figure-2 is a perspective view of a finished disk, and

Figure 3 is an edge view Of the disk shown in Figure 2. In the manufacture of disks in accordance with my. invention, I prefer to proceed as These disks to that of the coating must be relatively MATERIAL AND METHOD OF MAKING THE SAME.

follows: I first take graded abrasive grains of the proper size or grit for the workto be ground, and add a sufficient quantity of a resin solvent to coat the surface of the grains. I prefer to employ furfural as the coating proportion of approximately 30 cubic centimeters thereof to 1000 grams of grains if thelatter are of medium size or grit. For abrasive grains of thefiner grade, however, the amount of the solvent employed may be lOW as 25 cubic centimeters per 1000 grams of grains, while it may run as high as 40 cubic centimeters per 1000 grams of grains of the coarser grade. Furfural is an aldehyde which has the property of acting with the hexamethylenetetramine constituent of the redmanol to form also a resin of a character similar to redmanol resin. Having moistened the abrasive grains with a sufiicient all of their surfaces, I then mix redmanol in powdered form therewith. If the abra-' sive grains are of medium size or grit, a sufficient quantity of redmanol will be added to constitute approximately 10 per cent by weight of the mixture. The redmanol may, however, constitute from 7 to 15 per cent of the mixture, depending upon the grade of the abrasive grains, the finer grits requiring more of the resin than the coarser'grits. IVhen the resin is thus added to the moistened grains, the-furfural dissolves enough resin to coat the grains uniformly over their surfaces with the solution of furfural and resin, The furfural also tends to carry-the dissolx'ed binder into the pores of the grains.- In this way a good bond is obtained between the grains and binder, even with a comparatively dry mixture. The ingredients are mixed quickly to keep the mass from balling up, and they form a mass of quit e'dry consistency which can be readily spread in thin layers of great uniformity. This is not possible with wet mixtures.

After this mixture is thoroughly incorporated, it is placed in an iron mold of. the sha'perequired for the disk, such as is shown in Figure 1, evenly spread over the bottom plate 201 the mold, and molded under a solvent, using this substance inthe he materlal is then removed i a cloth backing 3 of the to the mixture,

grains dissolves ascertain amount of the red- 'manol and tends to carry it into the pores viously melted, such as is r firmly applied for same size as the disk, so that the disk can be supplied to the user in a form that can be fastened readilyto the base plate of the disk grinding machine.

very high working speeds, and the cloth backing supplies additional strength to the thin abrasive material, and forms an elastic cushion between .the abrasive material and the face plate. The cloth also serves to give a surface to which glue can be easily and fastening the disk tothe face plate. I, preferably use for mounting the disk on a cloth. backing a magnesia, oxychloride cement. I have found that this ce ment shows great adhesion between the redmanol body and the fabric, and is also unaffected by the binders which are commonly employed for cementing the disks to the iron face plate, and which may of soda.

An important lies in the fact that I am enabled to mold abrasive disksand abrasive wheels of exceedingly small thickness, there being no difliculty in making disks of large diameter be glue or silicate as thin as 3/64. inches.

Another advantageof my invention is that the substance furfural, which is preferably used for moistening the .grains, thoroughly wets all of the surfaces of the grains, so that when the powdered redmanol-is added this film of furfural of the grains, thus coating allof the surfaces of the grains with a solution of furfural and redmanol. This coating, after baking, forms a resin of substantially the 40 same composition as the principal binder. This adds greatly to the. perfection of the. bonding of the grains.

There are manyother advantages arising from this method of makin v abrasive disks. The disks are cheap to pro uce, because although made from. aresin, the mixture is molded cold and does not have to be prethe-case with mixtures of shellac, certain other phenolrresins and other elastic binders. Only one baking or heating of the disks in the oven is required, andthe disks do not have to be applied to their backings before'bei'ng sub-. jected to the baking, so that destruction of the backings, due to the baking temperature, is avoided. Moreover, a very open free-cut- .ting abrading material is produced, this .ma- 'terial possessing great strength and dura bility, such ,as is required for very diflicult grinding operations,

a cool cutting material and avoid drawing the temper of steel or otherwise affecting the material being ground.

These machines are operated at' I ."stantially as described. advantage of my invention on the ing and an abrading portion,

portion being formedfrom a substantially The material pro-. duced is waterproof and can be used on any operations where water is required to obtain While I have described my invention with particular reference to the manufacture of abrasive disks, to this particular use but may be employed with advantage for the making of other articles of bonded granular material, whether of an abrasive nature or not. For example,

the invention is also particularly applicable to the manufacture of a filtering medium,

the superior quality because by reason of of' the bond 'it is possible to reduce the amount of the binder to such an extent as to secure the desired high degree of porosity in the article without rendering the article mechanically Weak.

I claim: u

1. An article of bonded granular matethe invention is not limited I rial, formed from a mixture comprising a synthetic resinand grains having their surfaces moistened with a resin solvent, sub- 2. An article of bonded granular matephenol resln and grains having their surfaces moistened with furfural, substantially as described,

3. An article of'bonded granular material, formedfrom a mixture comprising a synthetic resin and grains having their sur-- rial, formed from a mixture comprising a 42. The method of making an article of bonded granular material, comprising moistening the surfaces of the-grains with a resin solvent and then mixing the moistened grains with a synthetic resin, as described. Y

substantially .5. The method of making an article of bonded granular material, comprising moistenlng the surfaces ofthe grains with furfural and then .mixing' the moistened grains with a phenol resin, substantially as de-' scribed.

G. The. method of making an article of bonded granular material, comprising moistening the surfaces of the grains with a1resin solvent, mixing the moistened-grains with a synthetic resin, forming the article from saidmixture, and heat treating it to harden the binder, substantially as described.

7. An abrasive article, formed from a compacted and baked mixture comprising a synthetic re'sin and abrasive grains whose surfaces have first been moistened with, a resinsolvent, substantially as described.

'8. An abrasive disk consisting of a backsaid abrading dry, compressed andbaked mixture comprismg. abrasive grains: moistened with a resin described.

9. An abrasive'disk consisting of aback ing and an abradmg portion, said 'abrading 15 per cent by wei ht of the mixture, substantially as descri ed.

11. The method of making abrasive articles which comprises moistening the surfaces of the grains with furfural, mixing the moistened grains with a phenol resin binder, molding the mixture under pressure, and' then heating it sufliciently to harden the binder, substantially as described.

12: The method of making abrasive articles which comprises moistening the surfaces of the grains with furfural, mixing the moisened grains with a phenol resin binder in the proportion of about 10 parts by weight of the binder to parts by weight" of the moistened grains, molding the mixture under pressure, and then heating it sufliciently to harden the binder, substantially as described.

13. The method of making abrasive articles which comprises moistening the surfaces of the grains with furfural, mixing the moistened grains with between 7 and 15 per cent by weight of aphenol resin binder,

molding the mixture under pressure, and thenheating it sufiiciently to harden the binder, substantially as described.

14. The method of making abrasive artis cles which comprises adding to abrasive grains furfural in the proportion of from 25 to 40 cubic centimeters of furfural to 1000 grams of the grains, mixing the moistened grains with a phenol resin binder, molding the mixture under pressure, and then heating it sufficiently to harden the binder, substantially as described.

15. The method of making abrasive disks which comprises moistening the surfaces of the grains with a resin solvent, mixing the ular article,

moistened grains with a phenol resin binder, molding the mixture under pressure into disk form, heating the disk sufliciently to harden the binder, and then cementing it to a backing, substantially as described.

16. The method of making abrasive disks which. comprises moistening the surfaces of the grains with furfural, mixing the mois- I tened grains with a phenol resin binder,

molding the mixture under pressure into disk form, heating the disk sufliciently to harden the binder, and then cementing'it a backing, substantially as described.

. 17. The method of making a bonded granular article which consists in moistening the granular material with a resin solvent, mixing a dry comminutedresin therewith, and forming a relatively dry mixture capable of being spread in thin layers with uniformity, then shaping the mixture and baking the same.

I 18. An'article composed of granular material and aresin binder characterized by the fact thatthe resin immediately adjacent the surfaces of the grains has been spread over I the surfaces of the grains in solution so that it is in intimate contact with the grain surfaces while the mass of the resin binder has been maintained in a substantially dry state so that the binder and the particles are evenly and uniformly distributed in the article.

19. The method ofmaking a bonded grancontaining granular "material and a resin binder which consists in intimately distributing the binder over the surfaces of the grains by means of a resin solvent applied to the surface of the grains only, and while maintaining the mass of the resin inder in a'substantially dry state so that the binder and particles are capable of being evenly and uniformly distributed, molding the/composition in a-relatively dry state, and baking the same. a

In testimony whereof I have hereunto set In hand.

y HARRY c. MARTIN. 

